Turning tools of the above generally mentioned type are usually used for machining workpieces of metal, preferably by parting, grooving and profile turning. For the turning operations, it is desirable to use as slender cutting inserts as possible, in order to generate the thinnest possible grooves, thereby minimizing material losses and energy consumption. This means that the front portion of the support part under the cutting insert, as well as the front finger of the tightening part above the cutting insert have to be designed utmost slender or thin to be accommodated in the groove in the workpiece recessed by the cutting insert.
As a consequence of, on one hand, the fact that the front portions of the support and tightening parts of the basic body have to be slender, and on the other hand the fact that the movable tightening part is connected to the rest of the basic body via a thin, elastic material portion serving as a joint, difficulties arise in cooling the cutting insert in an efficient way. Thus, the cooling of previously known grooving and parting tools, respectively, has been effected in an inefficient and almost provisional way, more precisely by two pipe conduits routed from the rear fixing part of the basic body (or a tool holder connected with the basic body), situated externally to the basic body, and ending in outlets situated far from the cutting insert. De facto, an upper conduit for cooling the cutting insert from above mouths approximately in flush with the topside of the tightening part, while a lower conduit for cooling the cutting insert from below mouths at a point situated approximately halfway between the cutting insert and the underside of the support part. In order to improve the cooling of the cutting insert and furthermore avoid the need of the space-requiring external pipe conduits and associated problems, attempts have been made to form the requisite cooling-liquid conduits in the form of internal channels in the proper basic body. However, these attempts have had limited success so far that internal channels having a sufficient cross-section area indeed have been producible in the support part stiffly integrated with the fixing part, but not in the pivotably movable tightening part, which, with the exception of the thin, elastic joint, is spaced-apart from the fixing part as well as the support part via open gaps. In other words, it has previously only been practically possible to provide undercooling of the cutting insert via internal cooling-liquid channels, but not overcooling.
The cooling of the previously known tools has been effected using large quantities of flushing low-pressure cooling liquid (about a pressure of 10 bar), in spite of the development of the cooling technique within the area of cutting machining increasingly being pushed in the direction of using high-pressure liquid. Thus, numerous tools for chip removing machining have recently been designed for cooling-liquid pressures within the range of 400-1000 bar or more.
The present invention aims at obviating the above-mentioned shortcomings of previously known cutting tools, in particular turning tools for, for instance, grooving and parting purposes, and at providing an improved tool. Therefore, an object is to provide a tool having the capability of cooling the cutting insert in an efficient way not only from below but in particular also from above, without the tool needing to be cluttered up with external conduit pipes for the cooling liquid. An additional object is to provide a turning tool having the capability of cooling the topside of the cutting insert by a highpressure liquid jet, which has accurate precision in respect of the point of impact thereof against the cutting insert. In particular, the invention aims at allowing the formation of a so-called hydraulic wedge between the chip surface of the cutting insert and the chip partly broken away, wherein the cooling effect of the jet of liquid even may be of secondary interest in comparison with the chip-breaking effect thereof. A parallel object of the invention is to provide an improved chip evacuation during grooving or parting by the tool. Yet another object of the invention is to provide a tool, the improved cooling and chip-forming capacity of which does not intrude on the capability of the tightening part to distinctly fix the cutting insert in the insert seat. In other words, a high-pressure cooling liquid or fluid should be introducible into the tightening part without detrimentally affecting the delicate joint between the tightening part and the rest of the basic body.